Many room vents connected to a home’s ventilation system have shutters on them to alter the direction air enters a space. These shutters can also be pushed to close the vent, leading people to believe that they can shut off heating or cooling to a room this way and save money. If the vent doesn’t have shutters, they may try putting an object in front of it to block it and achieve the same effect.
We’ll explain below why doing this doesn’t work, and why it creates problems for your HVAC system. But don’t despair—we’ll have some suggestions at the end for how you can better control home heating and cooling to increase energy efficiency.
Why Closing Vents Doesn’t Save Energy
The simple answer is because the HVAC system doesn’t use any less energy or produce less heated air when a room vent is closed. Just because the air doesn’t reach a room doesn’t mean it reduces how much energy was necessary to heat or cool it. Not only does this not save energy, it creates several problems that have the reverse effect.
The Air Balance Problem
Shutting room vents when the HVAC system is running causes an air imbalance inside the ventilation system. An HVAC system is designed to take in air through the return ducts and then vent the same amount of air out the supply ducts. With closed vents, less air can escape, meaning the HVAC system is pulling in more air than it vents out, and this increases air pressure in the ventilation system. Higher pressure will force the blower fan to work harder and lower energy efficiency—the exact opposite of what people think shutting vents will do.
The Leaking Duct Problem
An increase in air pressure brings with it another problem: a heightened chance of air leaks in the ducts. As the pressure rises, weak parts of the duct walls will start to develop small leaks, but even small leaks allow large amounts of air to escape when the pressure is high. This causes even more energy waste for the HVAC system.
Options for Zoning Your Home
There are ways you can lower the amount you spend on heating and cooling in your house by closing off rooms to the HVAC system. One of the most common methods is to have a zone control system installed. This is a way to “close the vents” to rooms without creating the pressure problems and waste. A zone control system uses a set of dampers to shut off airflow to specific rooms while allowing the excess air to flow elsewhere and the HVAC system to switch to a lower-power mode. We can retrofit existing systems for zone control or create zoning as part of a new system installation.
Another option is to use a different type of HVAC system: a ductless mini split. These systems use individual room air handlers to send heated/cooled air into the living space. Each air handler works independently, so you only need to run the ones in rooms that need it.
Reach out to us to find out more about how we can help your air conditioning and heating in Fresno, CA.
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